The present invention relates to a hydraulic controller that includes a housing structure, and a hydraulic drive unit provided with the said hydraulic controller.
A hydraulic drive unit that easily provides a driving force created by an oil pressure without laying hydraulic pipes if only an electric power source is present has been used, for example, for lifting work equipment of a special agricultural vehicle with respect to the cultivated ground, and in the future, the expansion of industrial application to many fields is anticipated.
The hydraulic drive unit is broadly made up of an actuator (usually, a “hydraulic cylinder” is used) and a hydraulic controller for operating (expanding and contracting in the case of the hydraulic cylinder) the actuator. The hydraulic controller includes an electric motor capable of rotating in a normal and a reverse direction, a hydraulic pump for sending hydraulic oil under pressure in the normal and reverse directions by means of the rotation of the electric motor, an oil tank for storing hydraulic oil in an enclosed space, a valve for controlling the flow of hydraulic oil in the normal and reverse directions among the hydraulic pump, the oil tank, and the actuator, and a housing (also referred to as a body block), which contains the hydraulic pump, the valve, and the like, and which is formed with an oil path therein.
The housing as described, for example, in Unexamined Japanese Patent Publication No. 11-29345 is formed into a block shape, and in one of the bottom surface portions (one bottom surface portion) thereof is formed a motor connecting portion. When the electric motor is connected to the motor connecting portion, the output shaft of the electric motor is fitted in a hole (fitting hole) formed in the housing, with the output shaft being connected to the driving shaft of the hydraulic pump.
However, in the configuration in which the output shaft of the electric motor is fitted in the hole formed in the housing and also connected to the driving shaft of the hydraulic pump, both of the fitting portion in which the electric motor is connected to the housing and the fitting portion in which the hydraulic pump is connected to the housing must be fabricated with high accuracy. Otherwise, because the output shaft of the electric motor is connected to the driving shaft of hydraulic pump later, the rotation center cannot be aligned, which poses a problem in that noise is generated when the motor and pump are driven, and an improper force acts in the interior and hence the assembly's service life is reduced. Also, a problem is present in that it is difficult to reduce the number of parts of the hydraulic drive unit and thereby to reduce its cost. Also, in the case where an electric motor housing for disposing the electric motor, a hydraulic pump housing for installing the hydraulic pump, and valves are present, because of a configuration such that these elements are connected to each other after a valve housing containing the valves has been manufactured separately, there arises a problem in that the manufacturing cost is high, and the reduction in the number of parts is similarly hindered.
In this respect, Unexamined Japanese Patent Publication No. 9-58438 has disclosed a configuration in which the electric motor housing and the hydraulic pump housing are integrated. In this case, however, the valve housing containing the valves is not integrated unlike the hydraulic drive unit.